With the development of the communication technologies, the M2M technology is gradually formed and rapidly developed. In brief, the M2M refers to transmitting data from one terminal to another terminal, i.e., a machine to machine interaction. But in a broad sense, the M2M may represent machine to machine, man to machine, machine to man, and mobile to machine connections and communications, and it covers all technologies and means for establishing communication connections between man, machine and system.
The application market of the M2M is quickly increasing all over the world. With the deepening of related technologies of communication device, management software, etc. and the decrease of the M2M product cost, the M2M service will gradually be mature. At present, the M2M has been applied to the fields such as safety monitoring, mechanical service, repairing service, vending machine, public transport system, fleet management, industrial process automation, motor machine and city informatization.
Generally, the M2M applications have various characteristics, wherein one type of very important characteristic is that many M2M applications have characteristics based on groups, and the communications having such group characteristics also include the following typical characteristics:                a large number of terminals;        a low mobility: the terminal does not move or just moves within a certain range;        the major service is the Mobile Terminated (MT) service;        if an MT service appears, a large number of terminals shall be simultaneously paged;the terminal shall make a subsequent response after receiving a paging message.        
Since the existed cellular network is mainly designed and optimized for the Human to Human (H2H) services such as voice, short message, etc., and the M2M has a large number of terminals, problems such as network congestion will easily be caused if a lot of M2M devices access the network.
Many organizations, such as the 3rd Generation Partnership Project (3GPP), have started to perform optimizations for the characteristics of the M2M applications, and proposed quite a few group paging solutions since most of the M2M applications have the group characteristics. The basic idea of group paging is that one group of device terminals share a group ID, and during paging, the group of device terminals are paged by carrying the group ID in the paging message. The corresponding paging is an individual paging which pages one device terminal.
For a paging of the MT service having the M2M group characteristics, the core network replaces the traditional individual paging with the group paging. First of all, the group ID is allocated. If a terminal device starts up and logins, the core network allocates a group ID to the terminal device according to the subscription data thereof; the group ID belongs to the core network hierarchy and the Non-Access Stratum (NAS), and it is also stored in the terminal device. Next, a group paging is carried out according to the allocated group ID. During group paging, the core network initiates a group paging request for devices having certain group characteristics in a certain paging area, wherein the group paging request includes the group ID of the group of devices; after receiving the group paging request, the access network directly uses the provided group ID of the core network to perform a group paging of all the devices of such type in the effective range. The paging area can be referred to as Routing Area (RA) in the Universal Mobile Telecommunications System (UMTS), and Tracking Area (TA) in the Long Term Evolution (LTE) system.
As can be seen from the above analysis, the grouping is only carried out in the core network rather than the access network. The group ID is “transparently transmitted” in relation to the access network, i.e., for the access network, the group paging and the individual paging have no difference, and its function is to package the paging request into a paging message and send it out, regardless of whether the message is sent for a group of devices or an individual device, and such information is only acquired by the device(s) per se and the core network.
Since the grouping strategy is only performed in the core network (CN) hierarchy, grouping is no longer carried out in the Radio Access Network (RAN). In relation to the access network, the core network cannot better acquire the distribution condition of the terminal devices, and even in the same paging area, the numbers of terminals contained in various cells of the access network may be quite different from each other. Thus, if the grouping is only carried out using the core network, the grouping may be unreasonable, e.g., too many terminals are existed in certain cells, which is adverse to the subsequent optimization of the group paging response.